Voice enhancement techniques, such as acoustic echo cancellation, are often implemented in communication systems, for example, to reduce echoes that result from the coupling between speaker(s) and microphone(s) at one end of a two-way communication.
FIG. 1 depicts an example two-way communication system 100. As shown in FIG. 1, a near-end communication device 102 used by a local user communicates with a far-end communication device 110 through networks 130. Specifically, within the near-end communication device 102, a microphone 104 may be used for capturing the local user's voices 114 and for producing an audio signal 112 to be transmitted to the far-end communication device 110. A speaker 106 located near the microphone 104 produces sounds 116 based on an audio signal 108 received from the far-end communication device 110. The sounds 116 produced by the speaker 106 may be picked up by the microphone 104 (e.g., directly or through reflection by walls or other objects) and may therefore be transmitted to the far-end communication device 110, which often results in echoes at the far-end communication device 110. Acoustic echo cancellation may be used to reduce the contribution from the speaker 106 in the audio signal 112 from the microphone 104.
FIG. 2 depicts an example two-way communication system 200 with acoustic echo cancellation. As shown in FIG. 2, in the two-way communication system 200, an acoustic-echo-cancellation (AEC) component 218 within a near-end communication device 202 is used to reduce echoes at a far-end communication device 210. Particularly, the AEC component 218 processes a recorded signal 212 from a microphone 204, using an audio signal 208 received from the far-end communication device 210 as a reference. The recorded signal 212 includes contribution from a speaker 206. The output signal 220 of the AEC component 218 is then transmitted to the far-end communication device 210 via networks 230.
As an example, the AEC component 218 may process the recorded signal 212 and generate the audio signal 220 according to the following formula:Vi=Vs Vr=Vs+Nf Vt=AEC{Vr,Vf}=AEC{Vi+Nf,Vf}  (1)where Vi represents an ideal audio signal to be transmitted, and Vs represents a local user's voices 214. In addition, Nf represents a noise signal, and Vr represents the recorded signal 212. Furthermore, Vt represents the output signal 220 of the AEC component 218, and Vf represents the audio signal 208, “AEC” in the formula (1) represents an acoustic-echo-cancellation function with two input signals (e.g., the audio signals 208 and 212).
FIG. 3 depicts an example communication terminal 300. As shown in FIG. 3, the communication terminal 300 (e.g., a cell phone) includes two modems 302 and 304. For example, the modems 302 and 304 may be used separately for independent two-way communications, or used together for a three-way audio conference. For example, an application processor 306 and the modem 302 are on a same chip 308, and the modern 304 is on a different chip. An acoustic-echo-cancellation (AEC) component may be included in each of the modems 302 and 304.